Database column types

Simple variables and record structures can be defined from database columns types.

Variables defined with the LIKE keyword get the same data type as the table column of a database schema.

Important: Database schema files are generated with the fgldbsch tool. Column data types are read from the schema file during compilation. Make sure that your schema files correspond exactly to the production database.

For example:

SCHEMA stores
DEFINE cust_name LIKE customer.cust_name
MAIN
  DEFINE rec_cust RECORD LIKE customer.*
  ...
END MAIN

A SCHEMA statement must define the database name identifying the database schema files to be used.

Alternatively, specify the database schema file followed by a colon, before the table name. This allows you to use several database schemas at the same time:

DEFINE rec_city      RECORD LIKE base:city.*
DEFINE rec_country   RECORD LIKE base:country.*
DEFINE rec_customer  RECORD LIKE orders:customer.*
DEFINE rec_item      RECORD LIKE stock:item.*

At runtime, a program typically connects to a single database source. Using multiple database schemas is a programming feature.

The database schema files must exist and must be located in one of the directories specified in the FGLDBPATH environment variable.

For CHAR/VARCHAR types, the size in the .sch file, the size in the .sch file is expressed in character units, and is then interpreted by the compiler as a number of bytes or characters, depending on the FGL_LENGTH_SEMANTICS environment variable as when using directly CHAR(N) or VARCHAR(N). For more details, see Extracting database schemas.

When using database views, the column cannot be based on an aggregate function like SUM().

If LIKE references a SERIAL column, the variable will be defined with the INTEGER data type. If LIKE references an INT8, SERIAL8 or BIGSERIAL column, the variable will be defined with the BIGINT data type.

The table qualifier must specify owner if table.column is not a unique column identifier within its database, or if the database is ANSI-compliant and any user of your application is not the owner of table.